Abstract: The traditional high-temperature sterilization process often leads to deteriorated texture and reduced water-holding capacity (WHC) in prepared meat products. To improve the processing quality of prepared pork slices, a two-stage heating method was employed, in which a low-temperature preheating step (45–60 °C for 1–3 h) was introduced before high-temperature sterilization at 121 °C. Conventional heating (100 °C for 30 min followed by 121 °C for 5 min) was used as the control. The shear force, centrifugal loss, free-water mobility, and myofibrillar fragmentation index (MFI) of the pork slices were determined, together with the total sulfhydryl content, surface hydrophobicity, α-helical content, and intrinsic fluorescence intensity of myofibrillar proteins. Changes in protein band patterns were also examined using sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and Pearson correlation analysis was performed between the major quality attributes and protein-related parameters. Compared with the conventional heating control, the two-stage heating treatments resulted in lower shear force, centrifugal loss, free-water mobility, and MFI, as well as higher α-helical content, total sulfhydryl content, and intrinsic fluorescence intensity. Among the two-stage heating treatments, preheating at 55 °C for 2 h resulted in the lowest shear force, centrifugal loss, and MFI. SDS–PAGE patterns showed that the actin bands in the low-temperature preheated groups were more distinct than those in the control group. Surface hydrophobicity was significantly higher in the low-temperature preheated groups than in the control group (P < 0.05). Pearson correlation analysis showed significant positive correlations among shear force, centrifugal loss, and MFI (P < 0.01), whereas MFI was significantly negatively correlated with total sulfhydryl content (P < 0.05). Under the experimental conditions used in this study, the treatment involving preheating at 55 °C for 2 h exhibited relatively favorable overall quality characteristics. These findings demonstrate that two-stage heating can improve the tenderness and water-holding capacity of prepared pork slices and provide a reference for its application in the processing of prepared meat products.